Healthrider r60 stops when it reaches 4mph.

Unplug unit and remove the motor shroud you will have to do DC Amp Measurement.
Measure on the hot DC lead (usually red) going from the controller to the drive motor. If you have a simple multi-meter with a DC amp test setting the best way to test is to put the meter inline on the red motor lead with alligator clips. If you have a more expensive clamp meter, clamp the meter around the red motor wire. Run the machine at 2.5 MPH without a person on the belt. If the motor and drive system are healthy, you should have a reading in the 2-3 amp range. Then walk on the treadmill at the same speed. With a person of average size (around 200 lbs.) you should have a reading in the 6-8 amp range if the belt is good. The readings will fluctuate more with a load but you are looking for an average reading but you shouldn't see spikes above 10 amps. If the amp readings are high without a load, you could have a problem with high resistance in the motor, a bad bearing, or over-tightened belts. Regular readings without a load but high readings with a load indicate a worn belt and/or deck.